Oh, this is awesome. I remember a post recently about wanting more community activities on Lemmy, and /r/Place was one of the things I said I'd missed the most.

For those who want to participate and can't figure it out (since there's no instructions) -

• Follow the link to http://canvas.fediverse.events/
• Ignore the immediate pop-up - it's not important for contributing to the artwork. Just click the X and move on.
• Look at the bottom of the page, it should say, "You are not logged in" with a Login button. Click that button, follow the instructions. Don't worry, it will not ask you for your password - it will ask for your full Fediverse handle (including the @lemmy.instance part) and it will send you a code instead.
• Check the inbox of whatever username you entered to find a message with a 5-digit code. Go back to the Canvas page and put in the code.
• Click the "approve" button that pops up next.
• After that, you should be logged in. Now you can contribute! Find a spot you want to add to, pick a color from the bottom row, and go for it! Note that if you leave the page idle for a bit, you may be asked to connect again.

There's a cool-down counter in the bottom left of 30 seconds, after which you'll earn another pixel to place. You can have up to 6 pixels ready to go. Once you have 6 pixels, the countdown disappears until you place one. If you lose connection or have to sign in again, it will save the pixels you accumulated. In writing this post I went through the process again to make sure I got it right, and I still had 6 pixels to use when I reconnected.

There's also an Undo button that appears immediately after placing a pixel, but it only lasts for a few seconds. If you accidentally click a pixel onto the image when you're just trying to scroll around, that button is your friend.

Note: I am not affiliated with this project in any way. I'm just sharing what I learned because it wasn't intuitive and I figure others might need a little help getting started.

Edit: Corrected the cool-down time.